Self-adjusting and non-adjusting clutches are known. These clutches typically have a single pivoting connection between a pressure plate and a diaphragm spring. When a high energy event occurs in the clutch, it results in a high temperature gradient throughout the pressure plate. This causes the pressure plate to distort from a flat or concave shape to a convex shape creating a geometrical height change at the connection between the pressure plate and the diaphragm spring which results in a lower operating point of the clutch. The change in the operating point causes lower working loads and less torque capacity of the clutch. Moreover, the change in the height of the diaphragm spring causes lower working loads and less torque capacity of the clutch. Furthermore, the change in the height of the fingers of the diaphragm spring can cause issues at the vehicle system level, such as the clutch pedal not returning when the operator tries to re-engage the clutch.
One example of a self-adjusting clutch is shown, for example, in U.S. Pat. No. 6,405,846, the entire disclosure of which is hereby incorporated by reference. Other examples of self-adjusting clutches are shown, for example, in U.S. Pat. Nos. 4,207,972 and 4,228,883.
The self-adjusting clutch of U.S. Pat. No. 6,405,846, for example, is a friction clutch with a pressure plate that is axially movably, but non-rotatably coupled to a cover and is biased by a diaphragm spring to urge the friction linings of a clutch disc against a flywheel. The design is intended to ensure that when the friction clutch is engaged, the diaphragm spring remains at least nearly constantly biased upon the pressure plate regardless of the wear upon the friction linings and other parts.
Additionally, the self-adjusting clutch of U.S. Pat. No. 4,207,972, for example, discloses an automatic wear compensator, or rotatable pivot ring, for a clutch to compensate for normal wear of the clutch's frictions faces. The pivot ring is operatively connected to a pressure plate and adjusted through a series of camming surfaces on the pressure plate.
Moreover, the self-adjusting clutch of U.S. Pat. No. 4,207,972, for example, discloses an automatic wear adjuster, or pivot ring, for clutches to compensate for wear of the clutch's friction faces during use. The automatic wear adjuster includes an advancing ring which abuts a pressure plate, a fulcrum ring which is placed on top of the advancing ring, and an actuator mechanism. A series of camming surfaces are formed on the rings to adjust the distance between the surface of the clutch disc and the engaging surface of the pressure plate and a surface of a fulcrum ring.